Incorporation of Graphdiyne-Based sp-Carbon Into the First Coordination Sphere of a Metal Complex for the Electrocatalysis of Nitric Oxide to Ammonia.

Although metal‒carbon bonds are prevalent in organometallics, integrating carbon donors alongside nitrogen, oxygen, and sulfur heteroatoms into the first coordination sphere of metal complexes poses a considerable challenge. Here, graphdiyne-based sp-carbon atoms are incorporated into the first coordination sphere of the metal complex, yielding an asymmetric sp-C2-M-O2 (M = Cu, Co, Ni) coordination geometry. During synthesis, hydrogen-substituted graphdiyne (HsGDY) acts as a microporous polymeric ligand populated with periodically aligned diacetylene coordination sites, which spatially confine and arrange metal complexes within micropores featuring a dominant size of 1.5 nm. For the electrochemical NO reduction, the microporous framework of HsGDY, which is rich in sp-carbons, accelerates NO mass transport, enabling elevated NO surface coverage even under diluted NO feeding streams. The electron-donating sp-carbons synergize with oxygen to tune the electronic structure of Cuδ+ (1 < δ < 2), reducing the formation barrier of *HNO and thus achieving a high NH3 Faradaic efficiency of 91.8% and a yield rate of 0.44 mg h-1 cm2 at 0.1 V versus a reversible hydrogen electrode (RHE). This work identifies graphdiyne-based sp-carbon atoms as viable constituents of the first coordination sphere of metal complexes, breaking the reliance on nitrogen, oxygen, and sulfur heteroatoms for constructing nonaxial asymmetric coordination geometries.